Downlighting illumination systems are used in a wide variety of configurations for general lighting, task lighting, accent lighting, emergency lighting, hospitality lighting, restaurant lighting, hospital lighting, office lighting, retail lighting, corridor lighting, and the like. The overwhelming majority of collimated downlighting illumination systems are recessed in a false or lowered ceiling however variants may be embedded in a wall or carried by a framework that is connected to a solid ceiling. Such downlighting systems are highly desirable due to the flush mounted fit with the ceiling and their deployment have become commonplace in commercial lighting applications. Downlighting illumination systems are designed specifically around the type of illumination light source used such as incandescent lamps, Compact Fluorescent Lamps (CFLs), halogen lamps, high intensity discharge lamps and more recently LEDs to list only a few however they often exhibit poor beam qualities and cause unwanted lighting effects such as beam striation, glare, unattractive scallops, uneven beam illumination causing illumination hotspots or colour variations and in the case of LEDs fringing or shadowing effects due to multiple light sources.
Due to the increased concern of man-made climate change the majority of downlighting systems currently utilise CFL lamp technologies due to improved lumen per watt characteristics as compared with the incandescent bulb. However, CFL lamps are inherently an omnidirectional light source emitting light in all directions (except where the electrical connector attaches to the body of the gas filled tube) and this leads to a significant loss of light when utilised within a downlight system. Indeed, most CFL based downlighters are significantly inefficient in converting the light generated by the CFL lamp into useful or usable light that exits from the aperture of the downlighter due to holes within the reflector system to enable the attachment of CFL lamps to a power source, re-absorption of light reflected back into the CFL lamp and the reflector design efficiency. The degree by which the efficiency of a downlighter can be measured is called the Light Output Ratio (LOR) which is the proportion of luminous flux (lumens) from the lamp(s) which emerges from the fixture and is usually a number between 0 and 1. Other things being equal, a downlight fixture having a high LOR is more efficient than one with a lower LOR. Traditional CFL downlighters offer a range of LORs from 0.3 to 0.7 depending upon the quality of the fixture design, whether diffusers are utilised and the intended beam angle and downlighter exit aperture. The LOR of a CFL downlighter (and any other omnidirectional light source) will drop significantly as both the beam angle and exit aperture decrease making CFL based downlights an inefficient means of providing high quality collimated light.
Downlighters based on LEDs which are inherently directional light emitting sources provide a significant LOR advantage over CFL based systems as the light emitted from LEDs are usually in a beam angle range from 10 degrees to 140 degrees. Unfortunately, LED based systems usually require an array of LEDs to be present in order to meet the desired number of lumens output from the lighting fixture. Such an LED array creates significant fringing and shadowing due to overlapping beam outputs from each individual LED in the array which often renders the light beam output from an LED unattractive. In addition, as the LED emitters have a small apparent size they often exhibit strong glare characteristics which is highly undesirable. In order to reduce such problems with LED based downlighters a secondary Total Internal Reflecting (TIR) collimating lens is placed above each LED to help collimate the output and then a diffuser is placed on top of this to help reduce glare. Although the TIR optics and diffuser increases the apparent source size of the LED emitting area the source sizes are still relatively small compared to the exit aperture of the downlighter and hence individual areas of bright light corresponding to individual LEDs in the array can be seen when looking directly at the downlighter exit aperture. The use of such an LED optical system still does not provide a quality beam output, increases optical losses in the system which is not desirable and adds costs to the manufacture of such a system. Other issues with LED based downlighters include significant variations in CCT and CRI of the fixture due to thermal management issues and binning of LEDs. LEDs are affected significantly by temperature and both the intensity and colour light output may change when operating temperatures vary making it difficult to maintain a constant intensity and colour output. This variation in both colour and temperature is highly undesirable and makes it exceptionally difficult to colour or intensity match groups of individual fixtures. Recent improvements in LED binning have still not solved the problems making LED based luminaires unappealing to the consumer. The CRI of today's high brightness white LEDs are generally lower than conventional light sources such as CFLs due to a low relative level of red light in the White LEDs emission spectrum however some LED illumination systems employ a combination of white and red LEDs to increase the overall CRI of such a system. Unfortunately, the spatial position of both the red and white LEDs are critical to achieve a quality beam output which is very difficult to obtain with LED arrays.
Downlighting luminaires, such as that provided by the invention, should also be easily assembled, installed and connected to power systems without the need for specialist tools. Still further, collimated downlighting illumination systems as herein described must be capable of being easily maintained so that replacement of the lamp system or driver can be readily accomplished without the need for specialised training. Components must be readily accessible and conventional mounting hardware should be suitable for the illumination systems herein disclosed.
The downlighting luminaires configured according to the present invention address the above requirements by utilising a single reflector system combined with an advanced lighting control system that extends the apparent source size of an LED or LED array to reduce or eliminate undesirable beam characteristics inherent in prior downlighting luminaires. Thus the invention provides a substantial advance in the art.